These are the commercial jet engines you see, like the Boeing 777, 747, Airbus A330 and A380s. Though there is a considerable reduction of the engine thrust, at these altitudes the lower drag associated with low air density means a more economical flight with a higher True Air Speed.
Crepitus in the knees may be caused by knee injuries such as meniscus tears. These are fairly common in people who play sports, jog, or run. A meniscus tear can cause crepitus as the joint moves. Chondromalacia patella is a dull ache behind the kneecap, usually caused by overuse or injury. There will be damage to the undersurface cartilage covering the kneecap.
Higginson R, Parry A (2011) Phlebitis: treatment, care and prevention. Nursing Times; 107: 36, early online publication. Peripheral venous catheter-associated phlebitis is caused by inflammation to the vein at a cannula access site. It can have a mechanical, chemical or infectious cause. Good practice when inserting a cannula, including appropriate choice of device and site, can help to prevent phlebitis.